A protective film may be used to prevent adhesion of contaminants such as dust and scratches on optical devices such as a polarizing plate, various plastic products, electric products, or automobiles. Suitable peel-off strength and antistatic property may be required for the protective film.
For example, when the protective film is peeled at a high speed in order to use a product or assemble another product, a relatively low peel-off strength (hereinafter, referred to as a “high speed peel-off strength”) is required. However, when the protective film is peeled at a low speed, the protective film may exhibit a suitable protective function with a relatively high peel-off strength (hereinafter, referred to as a “low speed peel-off strength”).
In addition, due to static electricity generated in peeling of the protective film, contaminants such as dust may be sucked, destruction of static electricity of a device, if it is an electronic product, or malfunction of the device may occur. Particularly, recently, as components are integrated due to supply of a computer and multifunctionalization of a liquid crystal TV or a mobile phone, problems caused by static electricity may be being further magnified.
Accordingly, there is an attempt to provide an antistatic function to a pressure-sensitive adhesive included in the protective film.
For example, there is an attempt to inhibit generation of static electricity by adding an ethyleneoxide-modified phthalic acid dioctyl plasticizer to a pressure-sensitive adhesive in the patent document 1. In addition, in the patent document 2, an organic salt is mixed to a pressure-sensitive adhesive, and in the patent document 3, a metal salt and a chelating agent are mixed to a pressure-sensitive adhesive. However, according to the above-methods, contamination caused by transfer of a pressure-sensitive adhesive component to a product to be protected occurs, static electricity generated in an early stage is difficult to be inhibited, and a low speed peel-off strength critical to obtain a protective function is too much reduced.